main: fix startup failing on Ubuntu 15.10/16.04
main: fix startup failing on Ubuntu 15.10/16.04

Since Ubuntu 15.10/16.04 still uses Upstart to manage GUI session (not as init), when we directly launch Scylla on Ubuntu's GUI Terminal(not using systemctl or initctl), raise(SIGSTOP) mistakenly calls (Because GUI session has "UPSTART_JOB" environment variable, won't happen when running Scylla as systemd service).

To avoid this, we need to verify UPSTART_JOB == "scylla-server".
If it's part of GUI session UPSTART_JOB has to be "unity7", we need to avoid raise(SIGSTOP) in that case.

Fixes #1199

Signed-off-by: Takuya ASADA <4ebfb6f510af412d6e89fefa3ab96d9c8b5e3fff@scylladb.com>
Message-Id: <1480620421-28967-1-git-send-email-4ebfb6f510af412d6e89fefa3ab96d9c8b5e3fff@scylladb.com>

duarten/scylla,avikivity/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,raphaelsc/scylla,duarten/scylla,duarten/scylla,raphaelsc/scylla,avikivity/scylla,avikivity/scylla,raphaelsc/scylla